Large span pre-cast concrete arch structures are often used in road building and the like. As used herein, the term "large arch structure" will mean an arch structure large enough for pedestrian or vehicular passageways, parking or large enough to support vehicle traffic over a roadway or a waterway as opposed to conduits and the like which enclose cables or drainage. These large structures need to be built from two or more arch segments due to transporting size and weight restrictions. Such arch segments are connected on site. A structure formed of twin-leaf arch sections is shown in FIG. 3.
Quite often, a rigid connection of precast concrete elements is made from reinforced cast-in-place concrete. The simplest and most commonly used joint for reinforcing steel is a lap splice. The present invention uses reinforced cast-in-place concrete for a joint and lap splices for reinforcement.
There are several methods presently employed to join twin-leaf arch sections together. As shown in FIG. 1, two cranes C1 and C2 are used in one method, and as shown in FIG. 2, one crane C3 and a scaffolding SC can be used.
With regard to FIG. 1, it can be seen that crane C1 will support section S1 of a pre-cast concrete twin-leaf arch structure 10 in place while crane C2 moves section S2 into place adjacent thereto, or vice versa as those skilled in the art will understand. Referring to FIG. 2, it will be seen that a single crane C3 will position section S2 in place with crown area CA2 supported on scaffold SC and then move section S1 into position with its crown area CA1 being placed in abutting contact with crown area CA2 on scaffold SC.
Quite often, the arch spans a body of water or a railway or highway in operation. The use of a central scaffolding is then not possible and two cranes are used for the installation. Using this method, an initial abutting contact is established between the twin units. Preferably, the joint includes mechanical elements for aligning and locking the two arch sections together when brought into abutting contact. Also, the joint should allow a controlled transmission of the abutting force and the use of a (temporary) connection for safety reasons.
For the same reasons that a central scaffolding may not be used, there is also a need that a cast-in-place concrete can be poured without an extra formwork to be installed.
In a prior art method of joining the twin-leaf arch sections, the crown areas are placed in abutting contact and filled in situ with concrete to complete the joint. As shown in FIGS. 4 and 5, the sections have crown areas, such as CA1 shown in FIG. 5 that include a stepped portion CA1S and a shoulder SH1 joining stepped portion CA1S to top surface TS1 of section S1. Section S1 has an end E1 that abuts end E2 of section S2 as indicated in FIG. 4 when the two sections are set up. A joint-forming portion JS is formed by the co-operating stepped sections CA1 and CA2 of sections S1 and S2 respectively, As shown in FIG. 3, portion JS is then filled in with concrete CT to complete the joint.
This method is meant to be used in connection with the erection method shown in FIG. 2, and in a method in which the joint concrete is poured and cured before the scaffolding is removed. If used with the method of FIG. 1, it is time consuming to properly orient the two arch sections with respect to each other. The joint is not locked when in abutting contact, and often, the uncontrolled transmission of the abutting force leads to spalling of the concrete.
Therefore, there is a need for a joint for precast concrete twin-leaf arch sections which is efficiently formed, can be formed over long spans and/or bodies of water or the like, allows a controlled transmission of abutting force and will retain the proper orientation of the two arch sections during the joint forming process.
In the case of a joint for large cast-in-place arches, the inventor has found that the joint needs to fulfill the following requirements:
The joint should be rigid and moment transmitting;
The joint should allow normal lap splices for reinforcement;
The joint should not require a form for pouring the cast-in-place concrete; and
A continuous (load distributing) connection of the individual arch rings in the longitudinal direction at the arch crown should be possible.
Therefore, there is a need for a joint for large cast-in-place concrete arch segments that will fulfil the just-mentioned requirements.